Clutch upgrade for 49' G80

[Sykes]

Hi Guys,

I have SRM clutches on my bitsa B33 BSA and a Newby on an old Norton.

They transform the gear change and are light in action. No slipping and no fettling to get them right.

Are there any recommended clutch upgrades for the Burman box?

Cheers,

Ed

[SPRIDDLER]

A '49 will have the Burman CP 'box which isn't known to be a slick operator but demobbed chaps probably weren't in so much of a hurry as are today's riders
At risk of seeming dismissive I can say that I've never had any problem with fettling the Burman clutch. A heavy action can be due to fitting the wrong h/bar lever having the span of the pivot bolt centre to nipple centre greater than the original 7/8". The conduit (outer) of a poor quality cable can crush and create friction as can a tortuously routed cable. It's often a revelation to experiment by running the cable 'outside everything' in a sympathetic routing. Obviously you couldn't ride it with cable flapping around but it will prove a point.
Unnecessary over-tightening of the springs will produce a heavy action. I adjust mine by having the least pressure that will stall the engine at a fast'ish tickover in first gear with the front wheel against a wall. The springs must be set so that all the plates lift equally.
A gummed up or rusty clutch thrust rod doesn't help so worth checking that.
I don't know of any commercial upgrades. Folk mention dry-running belt upgrades occasionally but overlook that the clutch basket rollers need oil.

BTW - if you don't have one the 96 page Owners Manual includes clutch and 'box set-up and you can find it here:
http://archives.jampot.dk/book/Owners_m ... Manual.pdf

HTH

[Groily]

To add a few words to what Spriddler has said, and make a few comparisons . . .

I have a 4 springer with Surflex plates on a swing-arm A10, which is very good (the 6 springers aren't so special, as is well known).
I have a diaphragm job and belt drive on a Norton which works well but is relatively heavy, and I have typical AMC three springers on a Mod 31 and a P11. They are 'OK' but do tend to get stressed in heavy traffic.

The smoothest and lightest in my shed . . . is the Burman on my Mod 20.

It's a GB box, while yours is the earlier CP, but I have to say in over 40 years the clutch has always been light in operation, slip-free and good at not developing loads of cable slack in traffic. (7/8th centres always.) The friction plates came from the club or from AMC Classic Spares and they last well. The bike has done several hundred thousand miles, so I've seen it through all stages of wear a good few times.

The CP box isn't maybe as nice in some ways as the GB - don't know what lubricant you have in there; nor how worn the selector mechanism might be? - but on the CP-equipped machines I have ridden, I never thought anything bad about the clutch side of it.

So I guess I'm saying 'not sure there's a good option for improvement to be had' or at least, 'Be careful what you wish for'! Because none of the others I have, with the possible exception of the Triumph-style one on the Beesa, is as light or smooth in operation.

You could probably graft something else on with quite a lot of work, just as folk contrive to get Suzi parts onto Beesas etc, but I would honestly start by making sure the one you have is set up as well as it can be and that the 'box itself is in good shape.

[GOLDSTAR]

I had to have a 3 spring AMC clutch on a Burman GB 'twas a lovely light action and many commented on it, managed to find and fit an AMC box with the same clutch much heavier action, I can only think the pivot mechanism for the Burman box was of better design thus making the pull lighter. kind regards
ps Hi Ya Groily,

[Groily]

HIYA Richard! Hope you're in top shape. Snow in Kent maybe? Quite a lot south of here, but just wet so far in my neck. Bloke was coming over with some bits for me this morning - but cried off after he looked out of his window and saw how white it was.

Interesting comment there. Maybe it is the lever mechanism on the AMCs. But however vaunted they be, I don't much like my own particular AMC clutches, also don't like the friction-lined drum feature a whole lot. Nor having to remember which one has inside and outside tangs on which plates, blah blah. The one in the P is quite new, the whole thing; the one on the 31 is old and cobbled together from parts - but they are pretty similar on the road, and not a patch on the Burman in heavy traffic.
(The Surflex plates in the Beesa were one of the best investments I've made. Quite a serious one in fact - but they are so brilliant at not sticking, you never ever have to free the plates prior to starting. And no slack in traffic. Very Nice - and also much commented on by those who borrow it.)
Cheers!

[39speedtwin]

Interesting the comments on the AMC clutch actuating mechanism, some years ago I converted the lever and ball mechanism on my N15 using the quick thread from a dolls head gearbox. This requires a new inlet to be made vertically in the cover, enables the clutch to be worked with one finger. Bike is now with a Sussex member.

[clive]

Hi Guys,
I have SRM clutches on my bitsa B33 BSA and a Newby on an old Norton.
They transform the gear change and are light in action. No slipping and no fettling to get them right.
Are there any recommended clutch upgrades for the Burman box?
Cheers,
Ed

Getting away from the AMC clutch I think there a number of issues with the CP box. Basically to get a clean change it needs to be done slowly. Apart from the suggestions from Spriddler you also need to look at the plates and the clutch sprocket. Are yours the CP type with outside tangs on the friction plates? If so its easy to clean u the ears and make sure there are no ridges in the slots in the sprocket basket. Easy to file back. If it is the later GB clutch there are no ears on the friction plate and it is a more difficult job to clean up the ridges in the sprocket basket. Get the final plate to pull out squarely.
The clutch can then be light and clean but the change will still be slow

[Sykes]

Thanks for the input guys.

Please excuse my ignorance regarding these models!

Is it possible to fit a later (better) gearbox into this frame? Its a complete bitza anyway and rideability will be above originality on in.

[Iron Head]

My ‘48 G80 Burman CP clutch is an absolute delight to operate and the prime reason I ride the bike so much versus the ‘killingly' heavy clutch on my Benelli 350 which is Z13 Kawasaki weight to operate! Arthritis isn't helping and this also affects my bass guitar fretting hand too - great getting old isn't it?!

[clive]

Thanks for the input guys.

Please excuse my ignorance regarding these models!

Is it possible to fit a later (better) gearbox into this frame? Its a complete bitza anyway and rideability will be above originality on in.

yes but the later AMC box will cost you. I wouldn't bother with the later Burman box, not much difference between the two in my experience. Exactly what are you disliking about your current box?